1. Field of the Invention
The present invention relates to a nitride semiconductor substrate. In particular, it relates to a nitride semiconductor substrate with a beveled edge.
2. Description of the Related Art
A conventional nitride semiconductor substrate is known that has a surface roughness Ra of 10 nm to 5 μm at an edge of a gallium nitride (GaN) substrate being circular viewed from its top.
The edge of the nitride semiconductor substrate is smoothed to thereby reduce the incidence of cracking, and enhance electronic device yields in an electronic device manufacturing process using that nitride semiconductor substrate.
The related art to the invention is, e.g., JP-A-2004-319951.
However, when forming on that nitride semiconductor substrate a micro-pattern using a photo mask with a stepper or a mask aligner in the electronic device manufacturing process, using the edge as a reference point for micro-pattern positioning may make it impossible to clearly observe the boundary between the substrate surface and edge under a microscope, and to precisely align the nitride semiconductor substrate relative to the photo mask.